powerpoint-presentatie 4/session iii - estuary...title powerpoint-presentatie author martin brinkman...
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Framework for yield gap analysis in grasslands
René Schils, Mats Höglind, Jantine van Middelkoop, Gertjan
Holshof, Koos Verloop, Bert Rijk, Gerrie van de Ven, Wim van
den Berg, Jan Rinze van der Schoot, Martin van Ittersum
Framework for yield gap analysis in grasslands
Background on yield gap concept
Yield gaps in grassland
Examples for the Netherlands and Norway
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Background on yield gap concept
Challenge to keep production on track with demand
Identify regions with unlocked yield capacity
Lagging attention for grasslands
● Grass is an internal farm product
● Animal farmers focus on their animals
● Methodological complexity
Theoretical production ecology
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Reducingfactors
•weeds•diseases•pests•pollution
Limitingfactors
•water•nutrients
Definingfactors
•Climate•CO2•variety
CR
OP
YI
EL
D
LimitedPotential ActualYi
eld
Gap
Van Ittersum & Rabbinge, 1997
Yie
ld G
ap
Quantifying...
• Benchmarks
YP Potential yield
YW Water-limited yield
YN Nitrogen-limited yield
YWN Water- and nitrogen-limited yield
• Farm yields
YA Actual yield
• Potential for improvement
YG Yield Gap
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Global Yield Gap Atlas
Rainfed wheat
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www.yieldgap.org
Yield gaps – general approach
Data
Daily weather
Soils
Crop types and management
Varieties
Experimental yields
Actual farm yields
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Identify unique zones
Agro-climatic conditions
Cropping systems
Quantify yield levels
Simulate YP, YW, YN, YWN
Calculate YA, YG
Yield gaps – additional challenges grasslands
Diversity in grasslands
● Function
● Botanical composition
● Management
Definition of productivity
● Gross yield in field – Net yield at field gate – Net animal intake
● DM yield – Digestible energy – Crude protein
Actual yield assessment
● Spatial and temporal data availability
● Definitions of grassland types
● Methods to estimate yields
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Yield gaps – Netherlands and Norway
Netherlands
Intensive dairy farming
975.000 ha
Mainly perennial ryegrass
2 silage cuts / 4 grazings
Empirical model (GRASS2007)
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Norway - Rogaland
Dairy, beef and sheep farming, various intensity
100.000 ha
Timothy or perennial ryegrass
3 silage cuts / 1 grazing
Process model (BASGRA)
Yield gaps - summary
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Spatial variation
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YA for different regions in NorwayYW for different soil types in SE Norway (LINGRA; Persson et al., 2015)
Sensitivity to grassland management
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Simulated (GRASS2007) YW with increasing cutting frequency
Calculated YA of grass for ~2000 farms in Nutrient Cycling Assessment projects
Framework for
yield gap
analysis in
grasslands
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